1. Field of the Invention
The present invention relates to the cultivation of mycobacteria and in particular leprosy bacilli and tubercle bacilli.
2. Description of the Prior Art
Leprosy is an ancient disease. There are over 12 million cases of leprosy in the world out of which about a fourth are present in India. No part of India is free from leprosy. The prevalence of the disease is high in southern and eastern States. The worst affected state is Tamil Nadu with approximately 800,000 patients. The other states where there are many sufferers are Andhra Pradesh, Binar and Orissa. In some districts 40 to 60 people out of every thousand suffer from leprosy.
About 25% of those having leprosy suffer from the infectious form of the disease.
Children are particularly susceptible to the disease. An assessment by the National Leprosy Control Programme has given an incidence rate of 42 per 1,000 in 8 school surveys in Tamil Nadu.
The causative organism of leprosy was discovered by Dr. Gerhard Henrik Armauer Hansen in 1873.
During the past 108 years scientists all over the world have been trying to grow the organism in the test tube but so far no one has succeded. Many claims have been made but none of them has been sustantiated.
Once the organism is grown in the test tube the whole outlook on this dreaded disease is bound to change since diagnosis will then become simple, rapid and reliable. At present, diagnosis depends on the examination of a smear of skin scraping. By the examination of the smear it is almost impossible to say whether the bacilli found are living or dead. To determine whether bacilli so obtained are living or dead mouse foot pads have to be inoculated and examined at periodical intervals. It takes almost a year before such examinations are conclusive.
However, if there were a suitable cultivation technique, the results could be obtained in a few days. If the organisms were found to be dead the treatment of the patient could be discontinued. This would be a great boon to the patient. Also, it may be possible to give a certificate to the patient that he is completely cured which is not possible now. This would be a great moral boost to the patient and a tremendous relief to his relatives.
Furthermore, once the organism is grown in a test tube drugs can be tested and the most suitable and effective of them can be prescribed for the patient.
With periodical examination of cultures grown from samples obtained from a patient it would be possible for the physican to follow the course of the disease in the patient and assess the value of the treatment given to him.
Only when the organism can be grown in the test tube can an anti-leprosy vaccine be prepared for preventing the disease among contacts of patients and for modifying the disease among those who are already infected.
Development of an anti-leprosy vaccine will be very useful in preventing or arresting the disease among children who are very susceptible to the infection. As Sir Leonard Rogers pointed out if all children are kept free from infection for the first 10 years of their lives, leprosy would almost or entirely die out of an endemic country within two generations.
Even today we do not know exactly how the disease spreads in the community. If a simple method of growing the organism were available it would be possible to decide on the route of infection and take suitable measures to prevent the disease among the population.
Furthermore, satisfactory cultivation of leprosy bacilli would greatly facilitate the testing of new drugs against the disease.
It is now recognized that some of the strains of leprosy bacilli isolated from patients are resistant to certain drugs.
At present, testing for sensitivity is done in mice. The animals are given the drug regularly and after a course of treatment infected in the foot pad with leprosy bacillus. If multiplication of bacilli is prevented in the foot pad it means that the organism is sensitive to the drug and that it can be used for treatment. This evaluation takes about a year. This requires an air-conditioned room for keeping the mice under observation and enormous labour and expense in feeding and looking after the infected mice for long periods.
With a suitable cultivation technique all this can be circumvented. There is no need to handle mice at all. The experiments may be carried out in ordinary tissure culture tubes and the results obtained in 4 or 5 days.
The common anti-leprosy drugs can be tested against bacilli infecting a particular patient and those which kill the organism can be selected for the treatment. If the bacilli are resistant to any drug that drug is not used in treatment.
The culture medium routinely used for the isolation of tubercle bacilli from sputum and other infective materials from patients is the Lowenstein-Jensen medium. This is a complex medium which contains contents of hen's eggs as an important constitutent. It takes about a month for the colonies of tubercle bacilli to grow in the medium. Therefore, the patient has to wait for about a month for confirmation of the diagnosis. The drugs routinely used for treatment of tuberculosis are streptomycin, paraaminosalicylic acid, isoniazid, rifampicin, clofazamine and thiacetazone.
The sensitivity of the organism from each patient to each of the above group of drugs varies. Some strains may be resistant to certain drugs but not others. Therefore, it is essential to find out to which drug the organism is susceptible. and administer that singly or in combination.
For this purpose a simple and rapid method of testing for drug sensitivity is essential. At present the organism is grown in the Lowenstein-Jensen medium which takes about 28 days. It is then tested in Lowenstein-Jensen medium containing different concentrations of each of the drugs. This takes another 28 days. Therefore, the treatment of the patient is delayed for about 2 months.